[Loops] FW: New AIA Loop Paper

[Joan T Schmelz (jschmelz)]

Dear Loop Lovers,

The attached paper on AIA multithermal loop analysis has just been published in ApJ Letters. Comments welcome!

ATMOSPHERIC IMAGING ASSEMBLY MULTITHERMAL LOOP ANALYSIS: FIRST RESULTS
by
J. T. Schmelz, J. A. Kimble, B. S. Jenkins, B. T. Worley, D. J. Anderson, S. Pathak, and S. H. Saar

ABSTRACT
The Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory has state-of-the-art spatial
resolution and shows the most detailed images of coronal loops ever observed. The series of coronal filters
peak at different temperatures, which span the range of active regions. These features represent a significant
improvement over earlier coronal imagers and make AIA ideal for multithermal analysis. Here, we targeted
a 171 Å coronal loop in AR 11092 observed by AIA on 2010 August 3. Isothermal analysis using the
171-to-193 ratio gave a temperature of log T ≈ 6.1, similar to the results of Extreme ultraviolet Imaging
Spectrograph (EIT) and TRACE. Differential emission measure analysis, however, showed that the plasma was
multithermal, not isothermal, with the bulk of the emission measure at log T > 6.1. The result from the isothermal
analysis, which is the average of the true plasma distribution weighted by the instrument response functions,
appears to be deceptively low. These results have potentially serious implications: EIT and TRACE results,
which use the same isothermal method, show substantially smaller temperature gradients than predicted by
standard models for loops in hydrodynamic equilibrium and have been used as strong evidence in support of
footpoint heating models. These implications may have to be re-examined in the wake of new results from AIA.

Regards,
Joan
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